1. Field of the Invention
The present invention relates to a variable heat generation viscous-fluid-type heat generator adapted to be used as a heat source incorporated in a heating system for heating an objective area. More particularly, the present invention relates to variable heat generating viscous fluid type heat generator adapted to be incorporated in a vehicle heating system for heating a passenger compartment of a vehicle.
2. Description of the Related Art
Japanese Unexamined (Kokai) Utility Model Publication No. 3-98107 (JU-A-3-98107) discloses a viscous fluid type heat generator adapted to be incorporated into an automobile heating system as a supplemental heat source. The viscous-fluid-type heat generator of JU-A-3-98107 is formed as a heat generator provided with a unit for changing a heat-generating performance. The heat generator of JU-A-3-98107 includes front and rear housings connected together to form a housing assembly in which a heat generating chamber for permitting a viscous fluid to generate heat, and a heat receiving chamber arranged adjacent to the heat generating chamber for permitting a heat exchanging liquid to receive the heat from the heat generating chamber, are formed. The heat receiving chamber in the housing assembly permits the heat exchanging liquid to flow therethrough from a liquid inlet port to a liquid outlet port formed in a portion of the housing assembly. Namely, the heat exchanging liquid is circulated through the heat receiving chamber and a separate heating circuit of the automobile heating system so as to supply the heat to the objective area, e.g., a passenger compartment of the automobile, during the operation of the heating system. The heat exchanging liquid flows into and out of the heat receiving chamber through the liquid inlet port and the liquid outlet port. The heat generator of JU-A-3-98107 further includes a drive shaft rotatably supported by bearings which are seated in the front and rear housings of the housing assembly. A rotor element is mounted on the drive shaft so as to be rotated together with the drive shaft within the heat generating chamber. The inner wall surface of the heat generating chamber and the outer surfaces of the rotor element define labyrinth grooves in which a viscous fluids such as silicone oil having a chain-molecular structure, is held to generate heat in response to the rotation of the rotor element.
The heat generator of JU-A-3-98107 has such a characteristic arrangement that upper and lower housings are attached to a bottom portion of the housing assembly to form a heat generation control chamber therein. The heat generation control chamber is formed as a volume-variable chamber having a wall consisting of a membrane such as a diaphragm.
The heat generating chamber communicates with the atmosphere via a through-hole bored in an upper portion of the front and rear housings of the housing assembly, and with the heat generation control chamber via a communicating channel arranged between the heat generation control chamber and the heat generating chamber. The volume of the heat generation control chamber is adjustably changed by the movement of the diaphragm which is caused by a spring element having a predetermined spring factor or an externally supplied signal such as a pressure signal supplied from an engine intake manifold of an automobile.
When the heat generator of JU-A-3-98107 is incorporated in a vehicle heating system and the drive shaft is driven by a vehicle engine the rotor element is rotated within the heat generating chamber, so that heat is generated by the viscous fluid, to which a shearing force is applied, between the inner wall surface of the heat generating chamber and the outer surface of the rotor element. The heat generated by the viscous fluid is transmitted from the heat generating chamber to the heat exchanging liquid, i.e., engine-cooling water circulating through the heat receiving chamber and through the heating system, to be carried by the water to a heating circuit of the heating system in order to warm an objective heated area such as a passenger compartment.
When heat transmitted from the vehicle heating system to the objective heated area is excessive, a vacuum is applied by the engine intake manifold to the diaphragm of the heat generation control chamber, and accordingly, the volume of the heat generation control chamber is increased due to the movement of the diaphragm. Therefore, the viscous fluid is withdrawn from the heat generating chamber into the heat generation control chamber to reduce heat generation in the viscous fluid within the heat generating chamber. Thus, the supply of heat from the viscous fluid type heat generator to the vehicle heating system is decreased to result in an reduction in the heat applied to the objective heated area.
On the other hand, when heat transmitted from the vehicle heating system to the objective heated area is too small, the diaphragm is moved by a combination of the spring force of the coil spring and the atmospheric pressure to reduce the volume of the heat generation control chamber. Therefore, the viscous fluid is supplied from the heat generation control chamber to the heat generating chamber to increase heat generation in the viscous fluid within the heat generating chamber. Thus, the supply of heat from the viscous fluid type heat generator to the vehicle heating system is increased to result in an increase in the heat applied to the objective heated area.
With the viscous fluid heat generator of JU-A-3-98107 incorporated in a vehicle heating system the heat generation control chamber is arranged below the heat generating chambers so that the viscous fluid may be withdrawn from the heat generating chamber into the heat generation control chamber due to its own weight when the heat generation by the heat generator should be reduced However, the withdrawal of the viscous fluid from the heat generating chamber into the heat generation control chamber cannot be smoothly achieved when the rotor element is being rotated within the heat generating chamber Specifically, since the heat generating chamber of the viscous fluid heat generator of JU-A-3-98107 has a labyrinth construction formed between the outer face of the rotor element and the inner wall surface of the heat generating chamber, it is very difficult for the viscous fluid to be withdrawn from the heat generating chamber into the heat generation control chamber via the labyrinth construction. Therefore, a rapid reduction in the heat generating performance of the viscous fluid type heat generator cannot be obtained Further, when the viscous fluid is withdrawn from the heat generating chamber into the heat generation control chamber, fresh air is introduced from an open port formed in the housing of the heat generator into the heat generating chamber so as to compensate for a vacuum occurring in the heat generating chamber. Thus, the viscous fluid is apt to come into contact with moisture contained in the fresh air when the reduction in the heat generating performance of the heat generator is carried out. Accordingly, the viscous fluid is rather quickly degraded by the moisture to reduce the heat generating efficiency of the viscous fluid to shorten the operating life of the viscous fluid type heat generator.